1. Field of the Invention
The present invention relates to a device for use in a camera system which includes an optical assembly having an image stabilizing unit for correcting image blur caused by shake in a camera or other optical apparatus.
2. Description of the Related Art
In cameras today, important settings including exposure and focus settings are all automated and even a person not familiar with camera operation is unlikely to fail to take a photograph.
Systems for preventing camera shake have been studied, and there are almost no factors that could cause a photographer to abort photographing.
Now a system for preventing camera shake is briefly discussed.
Camera shake during photographing is due to vibrations whose frequency falls within a range of 1 to 12 Hz. In order to photograph in image-blur free fashion even with camera shake at the moment of a shutter release, camera shake is detected and then a correction lens is displaced in response to the detected shake. To take a picture image-blur free, the camera shake needs to be accurately detected and variations in the optical axis of the camera need to be corrected accordingly.
Theoretically speaking, the vibration of a camera (camera-shake) is detected using vibration sensor means for detecting angular acceleration, angular velocity, angular displacement, the like, and camera shake sensor means that outputs angular displacement by electrically or mechanically integrating an output signal of the vibration sensor means. Image blur is thus, prevented by driving a correction optical system that decenters the optical axis of a photograph based on the information from these sensor mean.
The stabilization system using such vibration sensor means is now discussed referring to FIG. 8.
FIG. 8 shows the system for controlling image blur resulting from the vertical component 81p and horizontal component 81y of camera shake represented by arrows 81.
Shown in FIG. 8 are a lens barrel 82, and vibration sensor means 83p and 83y for detecting respectively the vertical component and horizontal component of the camera vibration; 84p and 84y denote respectively the directions of vibration. A correction optical assembly 85 (including coils 87p, 87y for imparting thrust to the correction optical assembly 85 and position sensors 86p, 86y for sensing the position of the correction optical assembly 85) is provided with a position control loop to be described later, and is driven with its target set to the output of the vibration sensor means 83p, 83y, thereby stabilizing an image on an image plane 88.
FIG. 9 is an exploded perspective view of an image stabilizing system (constructed of the vibration sensor means, the correction optical assembly, the coils, the position sensors and a variety of ICs) preferably used for the above purpose, and referring to FIGS. 9 through 18, the construction of the assembly is now discussed.
Rear projections 71a (one of three projections 71 not shown) of a base plate 71 (see its enlarged view in FIG. 12) are engaged with the lens barrel, and known barrel rollers are screwed into holes 71b to be secured to the lens barrel.
A glossily plated second yoke 72 of a magnetic material is secured to the base plate 71 by screws that pass through holes 72a of the yoke 72 and are screwed into screw holes 71c of the base plate 71. Permanent magnets (for shifting) 73 of neodymium or the like are magnetically attached to the second yoke 72. The direction of magnetization of each permanent magnet 73 is represented by an arrow 73a as shown in FIG. 8.
A correction lens 74 is attached with a C ring to a support frame 75 (shown in an enlarged view in FIG. 13). Coils 76p, 76y (shift coils) are forced to snap into place with the support frame 75 (the coils are not yet snapped in FIG. 13). Light emission devices (IRED) 77p, 77y are glued onto the rear surface of the support frame 75. Light rays emitted therefrom pass through slits 75ap, 75ay and reach position sensor devices (PSD) 78p, 78y. 
Each of holes 75b (at three positions) of the support frame 75 receives pins 79a, 79b, each having a spherical end and made of POM (polyacetal resin), and a bias spring 710 (as shown in FIGS. 10 and 12). The pin 79a is thermally caulked to the support frame 75 (the pin 79b is slidable in the direction of the hole 75b against the urging of the bias spring 710).
FIG. 10 is a cross-sectional view showing the image stabilizing system after it is assembled. The pin 79b, the bias spring 710, and the pin 79a in that order are inserted into the hole 75b of the support frame 75 in the direction of an arrow 79c (pins 79a, 79b are identical in shape), and the circular end portion 75c of the hole 75b is thermally caulked to prevent the pin 79a from coming off.
FIG. 11A is a cross-sectional view of the hole 75b viewed perpendicular to the page of FIG. 10, and FIG. 11B is a front view of the hole 75b viewed from the direction shown by the arrow 79c in FIG. 11A. Reference characters A through D in FIG. 11B correspond to depths A through D in FIG. 11A.
The back end of a blade portion 79aa of the pin 79a is engaged with and restrained by a surface A, and the circular end 75a is caulked, and the pin 79a is secured to the support frame 75.
Since a blade portion 79ba of the pin 79b is engaged with an abutment surface B, the pin 79b is prevented from coming out of the hole 75b under the urging of the bias spring 710.
When image stabilizing system is fully assembled, the pin 79b is engaged with the second yoke 72, and is thus prevented from coming out of the support frame 75. For convenience of assembling, the abutment surface B for locking purpose is provided.
As FIGS. 10 and 11 show the shapes of the support frame 75 and the holes 75b, the support frame 75 is manufactured using a simple split type molding technique in which a mold is simply pulled out in the direction of the arrow 79c, rather than a complex inner diameter slide molding technique, and accommodates high dimensional accuracy requirements.
The use of the pins 79a, 79b, identical to each other, reduces component cost, promotes error free assembling, and is advantageous from the component management point of view.
A shaft socket 75d of the support frame 75 is coated with fluorine-based grease, and receives one end of an L-shaped shaft 711 (non-magnetic stainless steel) (see FIG. 9). The other end of the L-shaped shaft 711 is received in a shaft socket 71d (similarly coated with the grease) formed in the base plate 71. With the three pins 79b resting on the second yoke 72, the support frame 75 is seated in the base plate 71.
As shown in FIG. 9, pins 71f (at three points) of the base plate 71 shown in FIG. 12 are received in alignment holes (at three points) 712a of a first yoke 712 shown in FIG. 9 while the first yoke 712 is engaged with abutment surfaces 71e (at five points) shown in FIG. 12 to be magnetically coupled to the base plate 71 (by means of magnetic force of the permanent magnets 73).
In this way the rear surface of the first yoke 712 is put into contact with the pins 79a, and the support frame 75 is interposed between the first yoke 712 and the second yoke 72 as shown in FIG. 10 so that the support frame 75 is registered in the direction of the optical axis of the camera.
The abutment surfaces of the first yoke 712 and the second yoke 72 and of the pins 79a, 79b mutually in contact are coated with fluorine-based grease, and the support frame 75 is slidably moved relative to the base plate 71 in a plane perpendicular to the optical axis.
The L-shaped shaft 711 permits the support frame 75 to be slidably supported relative to the base plate 71 in the directions shown by the arrows 713p, 713y only, thereby restraining a relative rotation (rolling) of the support frame 75 around the optical axis relative to the base plate 71.
The looseness permitted between the L-shaped shaft 711 and the shaft sockets 71d, 75d are set to be large in the direction of the optical axis so that the shaft sockets 71d, 75d may not override the restraint in the direction of the optical axis on the support frame 75 provided by the pins 79a, 79b interposed between the first yoke 712 and second yoke 72.
The first yoke 712 is covered with an insulating sheet 714. Mounted on the insulating sheet covered yoke 712 is a hard circuit board 715 (bearing the position sensor devices 78p, 78y, an amplifier IC, driving ICs for coils 76p, 76y) with its alignment holes 715b allowing pins 71h (at two points) of the base plate 71 to pass therethrough. At the same time, holes 715b of the circuit board 715 and holes 712b of the first yoke 712 are aligned and secured with holes 71g of the base plate 71 with screws.
The position sensors 78p, 78y are soldered to the hard circuit board 715 with the sensors aligned on the hard circuit board 715 with an instrument, and a flexible circuit board 716 is thermally bonded to the hard circuit board 715 with the surface 716a of the board 716 interfaced to the area 715c (see FIG. 9) of the rear side of the hard circuit board 715.
A pair of arms 716bp, 716by are extended from the flexible circuit board 716 in a plane perpendicular to the optical axis, and are engaged with lock portions 75eb, 75ey (see FIG. 13) of the support frame 75, and the terminals of the light emission devices 77p, 77y and the terminals of coils 76p, 76y are soldered to them.
The light emission devices 77p, 77y of IRED and coils 76p, 76y are driven by the hard circuit board 715 via the flexible circuit board 716.
The arms 716bp, 716by (FIG. 9) of the flexible circuit board 716 have respectively bent portions 716cp, 716cy. With their elasticity, the bent portions 716cp, 716cy lessen the load imposed on the arms 716bp, 716by when the support frame 75 moves in a plane perpendicular to the optical axis.
The first yoke 712 has elevated faces 712c formed through die cutting. The elevated faces 712c are directly put into contact with the hard circuit board 715 through notches 714a of the insulating sheet 714. The hard circuit board 715 has a ground trace on its surface in contact with the elevated faces 712c. By connecting the hard circuit board 715 to the base plate with screws, the first yoke 712 is grounded and is prevented from serving as an antenna which could pick up noise for the hard circuit board 715.
The mask 717 shown in FIG. 9 is aligned relative to the base plate 71 by pins 71h, and is affixed to the hard circuit board 715 using two-sided adhesive tape.
The base plate 71 is provided with a cutout 71i for a permanent magnet (see FIGS. 9 and 12), and the rear surface of the second yoke 72 is seen through the cutout 71i. A permanent magnet 718 (for locking) is assembled through the cutout 71i, and is magnetically coupled with the second yoke 72 (FIG. 10).
A coil 720 (for locking) is glued onto a lock ring 719 (see FIGS. 9, 10 and 14). The lock ring 719 has a lug 719a, the rear surface of which is provided with a bearing 719b (see FIG. 15). An armature pin 721 (see FIGS. 9 and 15) is inserted into an armature rubber bushing 722 and then inserted through the bearing 719b, an armature spring 723, and finally into an armature 724. The armature pin 721 is caulked to the armature 724.
The armature 724 is slidably moved relative to the lock ring 719 in the direction of an arrow 725 against the urging of the armature spring 723.
FIG. 15 is a view of the image stabilizing system viewed from behind in FIG. 9. As shown, the lock ring 719 is connected to the base plate 71 in a bayonet-mounting method, in which the lock ring 719 is pushed into the base plate 71 with the outer-circumferential notches 719c (at three points) of the lock ring 719 aligned with the inner-circumference projections 71g (at three points) and is then turned clockwise to lock into place.
The lock ring 719 is rotatable around the optical axis relative to the base plate 71. A rubber lock 726 is pressed into the base plate 71 (see FIGS. 9 and 15) in order to prevent the bayonet mount from being unlocked with the notches 719c of the lock ring 719 meeting the projections 71j. The lock ring 719 is thus permitted to rotate by an angle of xcex8 until a notch 719d is restrained by the rubber lock 726 (see FIG. 15).
The permanent magnet 718 (for locking) is attached to a locking yoke 727 made of a magnetic material (FIG. 9). The locking yoke 727 is attached to the base plate 71 with holes 727a (at two points) of the locking yoke 727 receiving pins 71k of the base plate 71 and with holes 727b (at two points) aligned with 71n (at two points) with screws.
The permanent magnet 718 on the base plate 71, the permanent magnet 718 on the locking yoke 727, the second yoke 72 and locking yoke 727 form a known closed magnetic path.
The rubber lock 726 is prevented from coming off because the locking yoke 727 is affixed by screws. For convenience of explanation, the locking yoke 727 is not shown in FIG. 15.
A lock spring 728 is extended between a hook 719e of the lock ring 719 and a hook 71m of the base plate 71 (FIG. 15) in order to urge clockwise the lock ring 719. An attracting coil 730 is loaded on an attracting yoke 729 (FIGS. 9 and 15). The attracting yoke 729 is secured to the base plate 71 at a hole 729a with a screw.
The terminals of the coil 720 and the attracting coil 730 may be four wires in twisted pair with Tetoron covering and are soldered to the cores 716d of the flexible circuit board 716.
ICs 731p, 731y (FIG. 9) on the hard circuit board 715 are amplifier ICs for amplifying the outputs of position sensor output terminals 78p, 78y. Their circuits are shown in FIG. 16 (the circuit of IC 731p only is shown here because both ICs 731p, 731y are identical).
Referring to FIG. 16, current-voltage converter amplifiers 731ap, 731bp convert, into voltages, currents 78i1p, 78i2p in position sensor 78p (including resistors R1, R2) generated by the light emission device 77p, and a differential amplifier 731cp determines and amplifies a differential between the outputs of the current-voltage converter amplifiers 731ap, 731bp. 
The light rays from the light emission devices 77p, 77y are directed to the position sensor devices 78p, 78y via slits 75ap, 75ay, respectively. When the support frame 75 moves in a plane perpendicular to the optical axis, the incident positions of the light rays to the position sensor devices 78p, 78y change.
The position sensor device 78p has a gain directivity in the direction of an arrow 78ap (FIG. 9), while the slit 75ap is shaped to diverge the light ray in the direction perpendicular to the arrow 78ap (namely in the direction of 78ay) and to converge the light ray in the direction of the arrow 78ap. Only when the support frame 75 moves in the direction of an arrow 713p, the balance between the currents 78i1p, 78i2p in the position sensor device 78p changes causing the differential amplifier 731cp to give an output according to the movement of the support frame 75 in the direction of the arrow 713p. 
The position sensor device 78y had a gain directivity in the direction of an arrow 78ay (FIG. 9), while the slit 75ay is shaped to diverge the light ray in the direction perpendicular to the arrow 78ay (namely in the direction of 78ap). The output of the position sensor device 78y changes its output only when the support frame 75 moves in the direction of an arrow 713y. 
A summing amplifier 731dp sums the outputs of the current-voltage converter amplifiers 731ap, 731bp (sum of the amounts of light received by the position sensor device 78p), and a driving amplifier 731ep drives the light emission device 77p in response to the sum signal.
The light emission device 77p changes its output light level in an extremely unstable manner due to temperature change and the like, and along with such changes, the absolute amount (78i1p+78i2p) of the currents 78i1p, 78i2p of the position sensor device 78p varies.
For this reason, the output of the differential amplifier 731cp indicating the position of the support frame 75 (78i1pxe2x88x9278i2p) also varies.
When the driving circuit controls the light emission device 77p so that the sum of the amount of light received is constant, no variations take place in the output of the differential amplifier 731cp. 
The coils 76p, 76y shown in FIG. 9 are located in the closed magnetic path formed of the first yoke 712 and second yoke 72. By causing a current to flow through the coil 76p, the support frame 75 is driven in the direction of the arrow 713p (under Flemming""s rule), and by causing a current to flow through the coil 76y, the support frame 75 is driven in the direction of the arrow 713y. 
The outputs of the position sensor devices 78p, 78y are amplified by ICs 731p, 731y, and the outputs of ICs 731p, 731y are used to drive the coils 76p, 76y. The support frame 75 is thus driven, changing the outputs of the position sensor devices 78p, 78y. 
If the direction of driving (polarity) of the coils 76p, 76y is set such that the outputs of the position sensor devices 78p, 78y gets smaller (negative feedback), the support frame 75 is stabilized when the outputs of the position sensor devices 78p, 78y driven by the coils 76p, 76y are almost zero.
A driving method in which a position sensor output is supplied in a negative feedback loop is called position control method. When a target value (for example, a shake angle signal) is input to ICs 731p, 731y from outside, the support frame 75 is faithfully driven toward the target value.
In an actual circuit arrangement, the outputs of the differential amplifiers 731cp, 731cy are sent to an unshown main circuit board via the flexible circuit board 716, and the outputs are analog-to-digital (A/D) converted there and then fed to a microcomputer.
In the microcomputer, the A/D converted signal is compared to a target value (shake angle signal), amplified and is subjected to phase lead compensation (for stabilizing position control) using a known digital filtering technique, transmitted through the flexible circuit board 716 to IC 732 (for driving the coils 76p, 76y). Based on the input signal, IC 732 drives the coils 76p, 76y in a known PWM method (Pulse Width Modulation), thereby driving the support frame 75.
The support frame 75 is slidably movable in the directions shown by the arrows 713p, 713y as already described, and stabilizes the camera through position control method. In consumer optical apparatuses such as cameras, however, the support frame 75 cannot be continuously controlled from the standpoint of power saving. With the camera left in no-control state, however, the support frame 75 is free to move in a plane perpendicular to the optical axis, and some preventive step has to be devised against an impact sound or even damage which may be generated when the support frame 75 (its mechanical end, more specifically the end of the lock ring) reaches its stroke limit.
A lock mechanism for locking the support frame 75 as such a preventive step is incorporated as described below.
Referring to FIGS. 15 and 17(A and B) the support frame 75 has, on its rear side, three radially extended projections 75f, and the ends of the projections 75f are engaged with the inner circumference 719g of the lock ring 719. The support frame 75 is thus restrained by the base plate 71 in all directions.
FIGS. 17A and 17B are rear views showing the working relationship of the lock ring 719 and support frame 75, and show major portions extracted from FIG. 15. For convenience of explanation, FIGS. 17A and 17B are drawn slightly differently from their actually assembled state. Cam sections 719f (at three points) shown in FIG. 17A are not fully longitudinally extended along the inner circumference of the lock ring 719 as shown in FIGS. 10 and 14, though they are not seen in FIG. 15.
As shown in FIG. 10, the coil 720 is located in the magnetic path between the permanent magnets 718, and by causing a current to flow through the coil 720, a torque is generated to rotate the lock ring 719 around the optical axis (twisted lead wires 720a shown in FIGS. 17A and 17B are connected at terminals 719h to an unshown flexible circuit board that is routed around the outer circumference of the lock ring 719 and connected to terminals 716e of the cores 716d of the flexible circuit board 716).
To drive the coil 720, an unshown microcomputer issues a command to a driver IC 733 on the hard circuit board 715 via the flexible circuit board 716 for control. IC 733 drives the coil 720 in PWM method.
Referring to FIG. 17A, the coil 720 is wound such that the coil 720, when energized, generates a torque for causing the lock ring 719 to rotate counterclockwise. The lock ring 719 thus rotates counterclockwise against the urging of the lock spring 728.
Before being energized, the lock ring 719, urged by the lock spring 728, remains stably in contact with the rubber lock 726.
When the lock ring 719 rotates, the armature 724 is put into contact with the attracting yoke 729 compressing the armature spring 723, thereby equalizing the attracting yoke 729 and the armature 724 in position. The lock ring 719 stops rotating as shown in FIG. 17B.
FIG. 18 is a timing diagram for lock ring driving.
The attracting coil 730 is also energized (730a) at the moment the coil 720 is energized (PWM-driven as indicated 720b) at an arrow 719i as shown in FIG. 18. When the armature 724 is in contact with and equalized with the attracting yoke 729, the armature 724 is attracted by the attracting yoke 729.
When the supply of power to the coil 720 stops at time 720c as shown in FIG. 18, the lock ring 719 attempts to rotate clockwise under the urging of the lock spring 728. The rotation of the lock ring 719 is restrained because the armature 724 is attracted by the attracting yoke 729. Since the projections 75f of the support frame 75 face the respective cam sections 719f (the cam sections 719f draw near in rotation), the support frame 75 is free to move within the clearance permitted between the projections 75f and the cam sections 719f. 
Although the support frame 75 is subject to gravity G (see FIG. 17B), the support frame 75 is prevented from falling because it is also controlled at time 719i in FIG. 18.
The support frame 75 is restrained by the inner circumference of the lock ring 719 during no-control state, but there remains a looseness corresponding to fit looseness between the projections 75f and the inner circumference 719g. The support frame 75 falls in the direction of gravity G by the looseness, and is thereby offset from the center of the base plate 71. For this reason, the support frame 75 is slowly shifted back to be in alignment with the center of the base plate 71 (center of the optical axis) from time 719i, for example, taking one second.
This quick shifting of the support frame 75 to the center causes image motion, which a photographer finds uncomfortable when it is seen through the correction lens 74. Furthermore, degradation resulting from the shifting of the support frame 75 is precluded even if an exposure is performed during the shifting. (For example, the support frame 75 is shifted by 5 xcexcm for xe2x85x9 second.)
More particularly, the outputs of the position sensor devices 78p, 78y are stored at time 719i shown in FIG. 18, control of the support frame 75 starts with the outputs set as a target value, and for a duration of one second, the support frame 75 is shifted toward the target value of the center of the optical axis that is set beforehand (refer to 75g in FIG. 18).
After the lock ring 719 is rotated (in unlock state), the support frame 75 is driven based on a target value from vibration sensor means (along with the movement of the support frame 75 back to the center), and stabilization operation thus starts.
To end the stabilization, image stabilization is set to be off at time 719j, the target value from the vibration sensor is not fed to correction driving means for driving correction means, and the support frame 75 is controlled so as to move to its centered position. The supply of power to the attracting coil 730 stops (730b). Since the attracting force of the yoke 729 for attracting the armature 724 is now absent, the lock ring 719 is rotated clockwise back to the state shown in FIG. 17A by the lock spring 728. The lock ring 719 touches and is restrained by the rubber lock 726, and the sound generated by the lock ring 719 is thus controlled at a low level.
A few moments later (20 ms later, for example), control of the correction driving means shown in the timing diagram in FIG. 18 ends.
FIG. 19 is a block diagram showing a circuit related to the image-blur correction or image stabilization function only of the camera equipped with the image stabilizing system.
The output of shake sensor means 2 is amplified by amplifier means 3, and then input to an A/D converting terminal of a microcomputer 1. The output of position sensor means 4 for sensing the position of the correction lens is amplified by amplifier means 5, and input to an A/D converting terminal of the microcomputer 1. The microcomputer 1 processes these input data and, outputs correction lens drive data to correction data driving means 6 to drive the correction lens for image stabilization. Lock/unlock driving means 7 drives an unlock coil and maintains an unlock state.
Generally speaking, the longer the focal length, the quantity of image blurring on the film plane arising from camera shake gets larger.
Suppose that an optional lens is available in a single-lens-reflex camera having a built-in image stabilizing system and that the optional lens allows an extender as a converter for lengthening the focal length. A more accurate image stabilization is required if a higher magnification extender is used. Image stabilization along with a high-magnification extender makes a xe2x80x9csea-sicknessxe2x80x9d effect more pronounced, and image stabilization conditions are accordingly adjusted.
Since the full-aperture F-number gets larger with a higher magnification extender, the shutter time gets slow. A satisfactory image stabilization effect may not be achieved.
When a high-magnification extender is mounted, a tripod is frequently used. In such a case, the switching off of image stabilization makes image blurring on the film plane less. If the image stabilization is switched off, however, the image stabilization function cannot be used at all even if the mounted extender is the one having a moderate magnification at which the image stabilization still sufficiently works.
According to one aspect of the present invention, a device for use in a camera system which comprises a camera, an optical characteristics modifying converter, and an optical unit having an image stabilizing unit for stabilizing an image in response to the output of a vibration sensor for detecting a shake in an apparatus, includes an activating means for activating the stabilization operation by the image stabilizing unit in response to a predetermined operation in a predetermined operation portion section on the camera, a determining means for determining whether an optical characteristics modifying converter without image stabilization function is incorporated in the camera system, and a decision means for deciding whether to perform the activating operation by said activating means based on the determination by said determining means, wherein the operation of the image stabilizing unit is determined by the incorporation of the converter.
According to another aspect of the present invention, a device for use in a camera system which comprises a camera, an optical characteristic modifying converter, and an optical unit having an image stabilizing unit for stabilizing an image in response to the output of a vibration sensor for detecting a shake in an apparatus, includes a determining means for determining whether the optical characteristics modifying converter is incorporated in the camera system, and a variable means for modifying frequency characteristics of the image stabilization operation in response to the determination by the determining means, wherein the operation of the image stabilizing unit is determined by the incorporation of the converter.